At present two major cardiovascular related morbidities, namely (a) heart failure and (b) shock (of all kinds) are lacking measurable indicator, diagnostic test, monitoring and follow-up capabilities (see a report of the American College of Cardiology/American Heart Association Task Force, Task Force on Practice Guidelines by Hunt S A, Abraham W T, Chin M H et al. “ACC/AHA 2005 Guideline Update for the Diagnosis and Management of Chronic Heart Failure in the Adult”, and the publication by Antonelli M, Levy M, Andrews P J D et al. “Hemodynamic monitoring in shock and implications for management”, International Concensus Conference, Paris, France, 27-28 Apr. 2006, Intensive Care Medicine, 2006; 4:575-590) wherein:                Heart failure refers herein to a global term for the physiological state (either an acute event or chronic course) in which cardiac output is insufficient in meeting the needs of the body (manifested as intolerability to perform different levels of physical activity). It is usually due to cardiac dysfunction (low cardiac output heart failure) but may also occur when the body's requirements for oxygen and nutrients are increased and the demand outstrips what the circulation can provide (e.g. severe anemia, Gram negative septicemia, beriberi, thyrotoxicosis, Paget's disease, arteriovenous fistulae, etc. (termed “high output cardiac failure”); and        Shock (also known as circulatory shock) refers herein to a life threatening condition of acute circulatory failure characterized by inadequate or inappropriately distributed tissue perfusion, which results in generalized cellular hypoxia. There are several shock types characterized by the underlying mechanisms (cardiogenic, hypovolemic, obstructive and distributive, etc.). However, regardless the underlying cause, all types of shock share identical manifestation of tissue level perfusion insufficiency. The mortality rate is very high and reaches 50%. All types of shock lack a satisfactory single diagnostic test or quantitative measure to evaluate the proceedings leading to shock and recognized pending or pre shock condition. In shock, either Cardiac Output (CO) or Systemic Vascular Resistance SVR (also known as total peripheral resistance) or both are severely decreased (see Serwin R, Audwin J G, Meena M. “Caring for critically ill patient in the emergency department”, Emergency Medicine Reports, 2011; 32:193-207).Existing Diagnostic Methods        
Early diagnosis is essential in order to intervene before irreversible consequences occur. Diagnosis is clinical and no specific test is available (see Serwin R, Audwin J G, Meena M. “Caring for Critically Ill Patient in the Emergency Department”, Emergency Medicine Reports, 2011; 32:193-207). Low blood pressure is not synonym to shock nor tachycardia. Shock Index (SI) which is the quotient of Systolic Blood Pressure (SBP) by Heart Rate (HR): SI=SBP/HR, was first introduced in 1967 (by Allgöwer M, Burri C., “The “Shock Index””, Dtsch Med Wochenschr 1967; 92:1947-1950) but was not implemented as a standard of evaluation and is still controversial (see Olerud S. Allgöwer M., “Evaluation and management of the polytraumatized patient in various centers”, World J. Surg. 1983; 7:143-148).
Invasive hemodynamic measurements are carried out in order to provide a diagnostic basis of the cardiovascular performance (see for example, Williams S G, Cooke G A, Wright D J, Parsons W J, Riley R L, Marshall P, Tan L B., “Peak exercise cardiac power output; a direct indicator of cardiac function strongly predictive of prognosis in chronic heart failure”, Eur Heart J. 2001; 22: 1496-1503) but are complicated costly and risky.
Furthermore, even when invasive measurements were taken the insight was neither satisfactory nor conclusive in cases of heart failure or shock (see Hunt S A, Abraham W T, Chin M H et al., “ACC/AHA 2005 Guideline Update for the Diagnosis and Management of Chronic Heart Failure in the Adult: a report of the American College of Cardiology/American Heart Association Task Force, Task Force on Practice Guidelines”, and Antonelli M, Levy M, Andrews P J D et-al., “Hemodynamic monitoring in shock and implications for management”, International Concensus Conference, Paris, France, 27-28 Apr. 2006, Intensive care Medicine, 2006; 4:575-590). Even cardiac output which is considered the most significant cardiovascular measure fails to predict accurately shock and heart failure (Antonelli M, Levy M, Andrews P J D et-al., “Hemodynamic monitoring in shock and implications for management”, International Concensus Conference, Paris, France, 27-28 Apr. 2006, Intensive care Medicine, 2006; 4:575-590).
In order to avoid invasive hemodynamic measurements on one hand and in order to provide hemodynamic information on the other hand, several indirect methods were suggested, for example, such as those disclosed in US Patent applications No. 2011/0152651 and 2005/0090753A1, U.S. Pat. No. 4,798,211, U.S. Pat. No. 5,178,151, and U.S. Pat. No. 7,054,679 among which, suggestions included measurements of heart rate variability through ECG, impedance cardiography, movement and acceleration measurements and analysis of the pulse pressure shape through dedicated equipment. However, as for today none of such methods became significant in the clinical practice. As of the impedance cardiography method for example (Packer M, Abraham W T, Mehra M R et-al., “Utility of impedance cardiography for the identification of short-term risk of clinical decompensation in stable patient with chronic heart failure”, Journal of the American college of Cardiology, 2006; 47:2245-2252) it remains in the research arena. As for heart rate variability (HRV) for example (Malik M et-al., “Heart rate variability, standards of measurement, physiological interpretation, and clinical use”, Task Force of the European Society of Cardiology, The North American Society of Pacing Electrocardiography) only seldom it is still used to predict myocardial infarction prognosis.
Acute phase monitoring systems of the severely ill patient (such as in intensive care or intermediate) are based on vital signs which induce an alarm which can be schematically classified into four main categories: 1. out of range of a single vital sign, 2. trend evaluation of a single vital sign, 3. wave related analysis (e.g. ECG, blood pressure or respiration), and 4. complex algorithms that involve multiple vital signs formulas predicting specific or non specific deterioration or negative outcome (Tarassenko L, Hann A, Young D. “Integrated monitoring and analysis for early warning of patient deterioration”, British Journal of Anaesthesia. 2006; 97:64-8). Several publications complaint that though alarm algorithm may accurately predict deterioration, it lacks in providing intelligence (Bloom J, Tremper K K, “Alarm in the intensive care unit: too much of a good thing is dangerous: is it time to add some intelligence to alarms?” Crit. Care Med., 2010; 38:702-703). Hence, alarm should include two characteristics: first, being accurate alarm validly predicting or detecting deterioration or negative outcome, the second (nevertheless important) is providing intelligence or insight either pointing toward a specific impairment or directing the staff towards the appropriate response. Most of the comprehensive alarms were proven accurate in prediction of deterioration, but lacked in pointing toward the underlying impairment hence left the staff unknowing where the impairment were exactly located. Unfortunately, this result sometimes in turning the alarm off by the frustrated staff (Bloom J, Tremper K K, “Alarm in the intensive care unit: too much of a good thing is dangerous: is it time to add some intelligence to alarms?” Crit. Care Med., 2010; 38:702-703, and Imhoff M, Kuhls S, “Alarm algorithms in critical care monitoring”, Anesth. Analg. 2006; 102:1525-37).
Therefore, it is an object of the present invention to provide a system which is capable to estimate the cardiovascular performance reserve (which is defined latter) through either invasive measurements or non invasive vital signs, and by which to indicate the cardiovascular status of a patient.
It is another object of the present invention to provide a single diagnostic test to quantitatively diagnose heart failure, to quantify its severity and to monitor severity dynamic in the short term and to follow changes of the long term.
It is yet another object of the present invention to provide a single diagnostic test to quantitatively diagnose shock and to quantify its severity and to monitor severity dynamic.
It is still another object of the present invention to provide an alarm system which is capable to estimate the cardiovascular performance reserve, through invasive measurement or non-invasive vital signs, and by which to indicates the cardiovascular status of a patient and as derived by this status to alarm while detecting cardiovascular deterioration, indication or prediction.
Other objects and advantages of the invention will become apparent as the description proceeds.